Juno Makes Earth Fly-By Before 3 Year Trip To Jupiter

It may seem counter-intuitive to launch a spacecraft on a path that intercepts Earth's orbit, but believe-it-or-not, scientists say it was the best route to Jupiter.

On Wednesday, NASA's Juno mission will be passing within about 350 miles of Earth's surface, which will be the closest it's been to our planet since leaving it in August 2011. This technique is similar to a slingshot, using the Earth to gain momentum for its trip to Jupiter.

"Juno will be really smoking as it passes Earth at a speed of about 25 miles per second relative to the sun. But it will need every bit of this speed to get to Jupiter for its July 4, 2016 capture into polar orbit about Jupiter," says Bill Kurth, University of Iowa research scientist and lead investigator for one of Juno's nine scientific instruments. "The first half of its journey has been simply to set up this gravity assist with Earth."

Juno will be using this opportunity to take video of Earth that has never been taken before. Scott Bolton, principal investigator for the Juno mission from Southwest Research Institute in San Antonio, says the NASA spacecraft will be making a movie of the Earth-moon system to show Earth spinning on its axis from a distance.

The spacecraft will be the first to orbit Jupiter over its poles, with Juno flying just above the cloud tops at a distance of about 1.75 million miles from Jupiter. Juno will orbit Jupiter about 33 times over the course of a year.

Juno will be exploring Jupiter's northern and southern lights by flying directly through the electrical current systems that generate them. The Waves instrument aboard the spacecraft will examine this phenomena by measuring radio and plasma waves.

"Jupiter has the largest and most energetic magnetosphere, and to finally get an opportunity to study the nature of its auroras and the role radio and plasma waves play in their generation makes Juno a really exciting mission for me," says Kurth.

The upcoming Jupiter mission will also be used to determine the amount of water and ammonia present in the planet's atmosphere, as well as to map out the planet's magnetic and gravity fields.

NASA is inviting amateur radio operators around the world to say "Hi" to Juno in a coordinated Morse Code message. The spacecraft's Wave instrument should be able to detect the message if enough people participate. The US space agency has details written out for radio operators to follow if they wish to participate in this experiment.